System for bypassing a power cell of a power supply

ABSTRACT

A system. The system includes a multi-winding device having a primary winding and a plurality of three-phase secondary windings, and a plurality of power cells. Each power cell is connected to a different three-phase secondary winding of the multi-winding device. The system also includes a first contact connected to a first input terminal of at least one of the power cells, a second contact connected to a second input terminal of the at least one of the power cells, and a third contact connected to first and second output terminals of the at least one of the power cells.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of U.S. Provisional PatentApplication No. 60/848,153, filed on Sep. 28, 2006.

NOT APPLICABLE BACKGROUND

This application discloses an invention that is related, generally andin various embodiments, to a system for bypassing a power cell in amulti-cell power supply.

In certain applications, multi-cell power supplies utilize modular powercells to process power between a source and a load. Such modular powercells can be applied to a given power supply with various degrees ofredundancy to improve the availability of the power supply. For example,FIG. 1 illustrates various embodiments of a power supply (e.g., an ACmotor drive) having nine such power cells. The power cells in FIG. 1 arerepresented by a block having input terminals A, B, and C; and outputterminals T1 and T2. In FIG. 1 a transformer or other multi-windingdevice 110 receives three-phase, medium-voltage power at its primarywinding 112, and delivers power to a load 130 such as a three-phase ACmotor via an array of single-phase inverters (also referred to as powercells). Each phase of the power supply output is fed by a group ofseries-connected power cells, called herein a “phase-group”.

The transformer 110 includes primary windings 112 that excite a numberof secondary windings 114-122. Although primary winding 112 isillustrated as having a star configuration, a mesh configuration is alsopossible. Further, although secondary windings 114-122 are illustratedas having a delta or an extended-delta configuration, otherconfigurations of windings may be used as described in U.S. Pat. No.5,625,545 to Hammond, the disclosure of which is incorporated herein byreference in its entirety. In the example of FIG. 1 there is a separatesecondary winding for each power cell. However, the number of powercells and/or secondary windings illustrated in FIG. 1 is merelyexemplary, and other numbers are possible. Additional details about sucha power supply are disclosed in U.S. Pat. No. 5,625,545.

Any number of ranks of power cells are connected between the transformer110 and the load 130. A “rank” in the context of FIG. 1 is considered tobe a three-phase set, or a group of three power cells established acrosseach of the three phases of the power delivery system. Referring to FIG.1, rank 150 includes power cells 151-153, rank 160 includes power cells161-163, and rank 170 includes power cells 171-173. A master controlsystem 195 sends command signals to local controls in each cell overfiber optics or another wired or wireless communications medium 190. Itshould be noted that the number of cells per phase depicted in FIG. 1 isexemplary, and more than or less than three ranks may be possible invarious embodiments.

FIG. 2 illustrates various embodiments of a power cell 210 which isrepresentative of various embodiments of the power cells of FIG. 1. Thepower cell 210 includes a three-phase diode-bridge rectifier 212, one ormore direct current (DC) capacitors 214, and an H-bridge inverter 216.The rectifier 212 converts the alternating current (AC) voltage receivedat cell input 218 (i.e., at input terminals A, B and C) to asubstantially constant DC voltage that is supported by each capacitor214 that is connected across the output of the rectifier 212. The outputstage of the power cell 210 includes an H-bridge inverter 216 whichincludes two poles, a left pole and a right pole, each with twoswitching devices. The inverter 216 transforms the DC voltage across theDC capacitors 214 to an AC output at the cell output 220 (i.e., acrossoutput terminals T1 and T2) using pulse-width modulation (PWM) of thesemiconductor devices in the H-bridge inverter 216.

As shown in FIG. 2, the power cell 210 may also include fuses 222connected between the cell input 218 and the rectifier 212. The fuses222 may operate to help protect the power cell 210 in the event of ashort-circuit failure. According to other embodiments, the power cell210 is identical to or similar to those described in U.S. Pat. No.5,986,909 and its derivative U.S. Pat. No. 6,222,284 to Hammond andAiello, the disclosures of which are incorporated herein by reference intheir entirety.

FIG. 3 illustrates various embodiments of a bypass device 230 connectedto output terminals T1 and T2 of the power cell 210 of FIG. 2. Ingeneral, when a given power cell of a multi-cell power supply fails inan open-circuit mode, the current through all the power cells in thatphase-group will go to zero, and further operation is not possible. Apower cell failure may be detected by comparing a cell output voltage tothe commanded output, by checking or verifying cell components, throughthe use of diagnostics routines, etc. In the event that a given powercell should fail, it is possible to bypass the failed power cell andcontinue to operate the multi-cell power supply at reduced capacity.

The bypass device 230 is a single pole single throw (SPST) contactor,and includes a contact 232 and a coil 234. As used herein, the term“contact” generally refers to a set of contacts having stationaryportions and a movable portion. Accordingly, the contact 232 includesstationary portions and a movable portion which is controlled by thecoil 234. The bypass device 230 may be installed as an integral part ofa converter subassembly in a drive unit. In other applications thebypass device 230 may be separately mounted. When the movable portion ofthe contact 232 is in a bypass position, a shunt path is created betweenthe respective output lines connected to output terminals T1 and T2 ofthe power cell 210. Stated differently, when the movable portion of thecontact 232 is in a bypass position, the output of the failed power cellis shorted. Thus, when power cell 210 experiences a failure, currentfrom other power cells in the phase group can be carried through thebypass device 230 connected to the failed power cell 210 instead ofthrough the failed power cell 210 itself.

FIG. 4 illustrates various embodiments of a different bypass device 240connected output terminals T1 and T2 of the power cell 210. The bypassdevice 240 is a single pole double throw (SPDT) contactor, and includesa contact 242 and a coil 244. The contact 242 includes stationaryportions and a movable portion which is controlled by the coil 244. Whenthe movable portion of the contact 242 is in a bypass position, one ofthe output lines of the power cell 210 is disconnected (e.g., the outputline connected to output terminal T2 in FIG. 4) and a shunt path iscreated between the output line connected to output terminal T1 of thepower cell 210 and a downstream portion of the output line connected tooutput terminal T2 of the power cell 210. The shunt path carries currentfrom other power cells in the phase group which would otherwise passthrough the power cell 210. Thus, when power cell 210 experiences afailure, the output of the failed power cell is not shorted as is thecase with the bypass configuration of FIG. 3.

The bypass devices shown in FIGS. 3 and 4 do not operate to disconnectpower to any of the input terminals A, B or C in the event of a powercell failure. Thus, in certain situations, if the failure of a givenpower cell is not severe enough to cause the fuses 222 (see FIG. 2) todisconnect power to any two of input terminals A, B or C, the failurecan continue to cause damage to the given power cell.

SUMMARY

In one general respect, this application discloses a system forbypassing a power cell in a multi-cell power supply. According tovarious embodiments, the system includes a multi-winding device having aprimary winding and a plurality of three-phase secondary windings, and aplurality of power cells. Each power cell is connected to a differentthree-phase secondary winding of the multi-winding device. The systemalso includes a first contact connected to a first input terminal of atleast one of the power cells, a second contact connected to a secondinput terminal of the at least one of the power cells, and a thirdcontact connected to first and second output terminals of the at leastone of the power cells.

According to other embodiments, the system includes a multi-windingdevice having a primary winding and a plurality of three-phase secondarywindings, and a plurality of power cells. Each power cell is connectedto a different three-phase secondary winding of the multi-windingdevice. The system also includes a first contactor connected to a firstinput terminal of at least one of the power cells, a second contactorconnected to a second input terminal of the at least one of the powercells, and a third contactor connected to first and second outputterminals of the at least one of the power cells.

DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are described herein by way ofexample in conjunction with the following figures.

FIG. 1 illustrates various embodiments of a power supply;

FIG. 2 illustrates various embodiments of a power cell of the powersupply of FIG. 1;

FIG. 3 illustrates various embodiments of a bypass device connected toan ouput of the power cell of FIG. 2;

FIG. 4 illustrates various embodiments of a bypass device connected toan ouput of the power cell of FIG. 2;

FIG. 5 illustrates various embodiments of a system for bypassing a powercell of a power supply;

FIG. 6 illustrates various embodiments of a system for bypassing a powercell of a power supply;

FIGS. 7-9 illustrate various embodiments of a bypass device;

FIG. 10 illustrates various embodiments of a system for bypassing apower cell of a power supply;

FIG. 11 illustrates various embodiments of a system for bypassing apower cell of a power supply;

FIG. 12 illustrates various embodiments of a system for bypassing apower cell of a power supply;

FIG. 13 illustrates various embodiments of a circuit for controlling abypass device;

FIGS. 14 and 15 show the per-unit DC current and power available forvarious per-unit DC voltages at V1 of the circuit of FIG. 13;

FIG. 16 illustrates various embodiments of a circuit for controlling abypass device;

FIG. 17 illustrates various embodiments of a circuit for controlling abypass device;

FIG. 18 illustrates various embodiments of a circuit for controlling abypass device; and

FIG. 19 illustrates various embodiments of a circuit for controlling aplurality of bypass devices.

DETAILED DESCRIPTION

It is to be understood that at least some of the figures anddescriptions of the invention have been simplified to focus on elementsthat are relevant for a clear understanding of the invention, whileeliminating, for purposes of clarity, other elements that those ofordinary skill in the art will appreciate may also comprise a portion ofthe invention. However, because such elements are well known in the art,and because they do not necessarily facilitate a better understanding ofthe invention, a description of such elements is not provided herein.

FIG. 5 illustrates various embodiments of a system 250 for bypassing apower cell (e.g., power cell 210) of a power supply. As shown in FIG. 5,the system 250 includes bypass device 252 connected to the outputterminals T1 and T2, a bypass device 254 connected to input terminal A,and a bypass device 256 connected to input terminal C. Although thesystem 250 is shown in FIG. 5 as having respective bypass devicesconnected to input terminals A and C, it will be appreciated that,according to other embodiments, the respective bypass devices may beconnected to any two of the input terminals A, B and C.

The bypass devices 252, 254, 256 may be mechanically-driven,fluid-driven, electrically-driven, or solid state, as is described inthe '909 and '284 patents. For purposes of simplicity, each bypassdevice will be described hereinafter in the context of a bypass devicewhich includes one or more electrically-driven contactors which areconnected to the output of a power cell. As described hereinafter, agiven bypass device may be embodied as a single-pole single-throw (SPST)contactor, a single-pole double-throw (SPDT) contactor, or a multi-polecontactor.

Bypass device 252 is a single pole double throw (SPDT) contactor, andincludes a contact 258 and a coil 260. The contact 258 includesstationary portions and a movable portion which is controlled by thecoil 260. The bypass device 252 operates in a manner similar to thatdescribed hereinabove with respect to bypass device 240 of FIG. 4. Thebypass device 254 is a single pole single throw (SPST) contactor, andincludes a contact 262 and a coil 264. The contact 262 includesstationary portions and a movable portion which is controlled by thecoil 264. The bypass device 256 is a single pole single throw (SPST)contactor, and includes a contact 266 and a coil 268. The contact 266includes stationary portions and a movable portion which is controlledby the coil 268. In general, in the event of a failure, bypass devices254, 256 disconnect the cell input power at substantially the same timethat bypass device 252 creates a shunt path for the current thatformerly passed through the failed power cell.

The condition associated with the creation of the described shunt pathand the disconnection of cell input power from at least two of the cellinput terminals may be referred to as “full-bypass”. When the fullbypass condition is present, no further power can flow into the failedcell. As described with respect to FIG. 2, the fuses 222 of the powercell may operate to help protect the power cell in the event of ashort-circuit failure. However, in certain situations (e.g., when faultcurrent is low), the fuses 222 may not clear quickly enough to preventfurther damage to the failed power cell. According to variousembodiments, the bypass devices 254, 256 are configured to act quickerthan the fuses 222, and the quicker action generally results in lessdamage to the failed power cell.

FIG. 6 illustrates various embodiments of a system 270 for bypassing apower cell (e.g., power cell 210) of a power supply. The system 270includes a single bypass device 272 which achieves the combinedfunctionality of the bypass devices 252, 254, 256 of FIG. 5. The bypassdevice 272 is a multi-pole contactor which includes a first contact 274connected to the output terminals T1 and T2 of the power cell, a secondcontact 276 connected to the input terminal A, and a third contact 278connected to the input terminal C. Each of the contacts 274, 276, 278include stationary portions and a movable portion. Although the secondand third contacts 276, 278 are shown in FIG. 6 as being connected toinput terminals A and C, it will be appreciated that, according to otherembodiments, the second and third contacts 276, 278 may be connected toany two of the input terminals A, B and C. The bypass device 272 alsoincludes a single coil 280 which controls the movable portions of thecontacts 274, 276, 278.

FIGS. 7-9 illustrate various embodiments of a bypass device 300. Thebypass device is a multi-pole contactor, and may be identical to orsimilar to the bypass device 272 of FIG. 6. The bypass device 300includes a first contact which includes stationary portions 302, 304 andmovable portion 306, a second contact which includes stationary portions308, 310 and a movable portion 312, and a third contact which includesstationary portions 314, 316, 318, 320 and a movable portion 322. Thebypass device 300 also includes a coil 324 which controls the movableportions 306, 312, 322 of the first, second and third contacts. Thestationary portions 304, 310 of the first and second contacts may beconnected to any two of the input terminals A, B and C of a power cell.The stationary portions 314, 318 of the third contact may berespectively connected to the output terminals T1 and T2 of a powercell. The movable portions 306, 312, 322 of the first, second and thirdcontacts are shown in the normal or non-bypass position in FIGS. 7 and8, and are shown in the bypass position in FIG. 9.

As shown in FIG. 7, the bypass device 300 also includes electricalterminals 326 connected to the coil 324, a steel frame 328 whichsurrounds the coil 324, a first insulating plate 330 between the steelframe 328 and the stationary portions 304, 308, 310, 312 of the firstand second contacts, a second insulating plate 332 between the steelframe 328 and the stationary portions 314, 316 of the third contact, andfirst and second support brackets 334, 336. The bypass device 300further includes a non-magnetic shaft 338 which passes through the coil324, through openings in the steel frame 328, through respectiveopenings in first and second insulating plates 330, 332, and throughrespective openings of the first and second support brackets 334, 336.

Additionally, the bypass device 300 also includes a first biasing member340 between the first support bracket 334 and a first end of thenon-magnetic shaft 338, a second biasing member 342 between the secondsupport bracket 336 and a second end of the non-magnetic shaft, and aposition sensing device 344 which is configured to provide an indicationof the position (bypass or non-bypass) of the movable portions 306, 312,322 of the first, second and third contacts.

Although not shown for purposes of simplicity in FIGS. 7-9, one skilledin the art will appreciate that the bypass device 300 may furtherinclude a plunger (e.g., a cylindrical steel plunger) which can travelaxially through an opening which extends from the first end of the coil324 to the second end of the coil 324, permanent magnets capable ofholding the movable portions of the contacts in either the bypass or thenon-bypass position without current being applied to the coil 324, afirst insulating bracket which carries the moving portions 306, 312 ofthe first and second contacts, a second insulating bracket which carriesthe moving portion 322 of the third contact, etc.

In operation, permanent magnets (not shown) hold the plunger in either afirst or a second position, which in turn holds the movable portions306, 312, 322 of the contacts in either the non-bypass position or thebypass position. When the electrical terminals 326 receive pulses ofcurrent, the pulses of current are applied to the coil 324, therebygenerating a magnetic field. Depending on the polarity of the appliedpulse and the position of the plunger, the applied pulse may or may notcause the plunger to change its position. For example, according tovarious embodiments, if the plunger is in the first position and themovable portions 306, 312, 322 of the contacts are in the non-bypassposition, a positive current pulse will change the plunger from thefirst position to the second position, which in turn changes the movableportions 306, 312, 322 of the contacts from the non-bypass position tothe bypass position. In contrast, if a negative current pulse isapplied, the plunger will stay in the first position and the movableportions 306, 312, 322 of the contacts will stay in the non-bypassposition.

Similarly, according to various embodiments, if the plunger is in thesecond position and the movable portions 306, 312, 322 of the contactsare in the bypass position, a negative current pulse will change theplunger from the second position to the first position, which in turnchanges the movable portions 306, 312, 322 of the contacts from thebypass position to the non-bypass position. In contrast, if a positivecurrent pulse is applied, the plunger will stay in the second positionand the movable portions 306, 312, 322 of the contacts will stay in thebypass position.

FIG. 10 illustrates various embodiments of a system 350 for bypassing apower cell (e.g., power cell 210) of a power supply. The system 350 issimilar to the system 250 of FIG. 5. The system 350 includes a firstcontact 352 connected to the output terminals T1 and T2 of the powercell, a second contact 354 connected to the input terminal A of thepower cell, and a third contact 356 connected to the input terminal C ofthe power supply. Each of the contacts 352, 354, 356 include stationaryportions and a movable portion. Although the second and third contacts354, 356 are shown in FIG. 10 as being connected to input terminals Aand C, it will be appreciated that, according to other embodiments, thesecond and third contacts 354, 356 may be connected to any two of theinput terminals A, B and C.

The system 350 also includes a first coil 358 which controls the movableportions of the first contact 352, a second coil 360 which controls themovable portion of the second contact 354, and a third coil 362 whichcontrols the movable portion of the third contact 356. According tovarious embodiments, the coils 358, 360, 362 are embodied as contactorcoils. According to other embodiments, the coils 358, 360, 362 areembodied as magnetic latching coils which do not need to have continuouspower applied to the coils in order to hold the plunger in its first orsecond position and/or to hold the moving portions of the contacts 352,354, 356 in the non-bypass or bypass position. The first contact 352 andthe first coil 358 may collectively comprise a first contactor, thesecond contact 354 and the second coil 360 may collectively comprise asecond contactor, and the third contact 356 and the third coil 362 maycollectively comprise a third contactor.

The system 350 further includes a first local printed circuit board 364in communication with the first coil 358, a second local printed circuitboard 366 in communication with the second coil 360, and a third localprinted circuit board 368 in communication with the third coil 362. Eachof local printed circuit boards 364, 366, 368 are configured to controlthe respective movable portions of the contacts 352, 354, 356 via therespective coils 358, 360, 362. In general, each of the local printedcircuit boards 364, 366, 368 are configured to receive commands from,and report status to, a master control device (e.g., master controlsystem 195 of FIG. 1) that is held near ground potential. Each of thelocal printed circuit boards 364, 366, 368 are also configured todeliver pulses of energy to the respective coils 358, 360, 362 as neededto change the position of the movable portions of the respectivecontacts 352, 354, 356, and to recognize the position of the movableportions of the respective contacts 352, 354, 356. Each of the localprinted circuit boards 364, 366, 368 may obtain control power from theinput lines which are connected to input terminals A, B, C of the powercell. As shown in FIG. 10, one or more position sensing devices (labeledPSD in FIG. 10) may be utilized to provide the local printed circuitboards 364, 366, 368 with the respective positions of the movableportions of the contacts 352, 354, 356. According to variousembodiments, the position sensing devices may be embodied as switchingdevices, hall effect sensors, optical sensors, etc.

For embodiments where the coils 358, 360, 362 are latching coils, thelocal printed circuit boards 364, 366, 368 may each include a DCcapacitor which can store enough energy to switch the plunger and/or themovable portions of the respective contacts 352, 354, 356 betweenpositions. Each of the local printed circuit boards 364, 366, 368 mayalso include a power supply which restores the stored energy after aswitching event, using AC power from the input lines connected to theinput terminals A, B, C of the power cell.

FIG. 11 illustrates various embodiments of a system 370 for bypassing apower cell (e.g., power cell 210) of a power supply. The system 370 issimilar to the system 350 of FIG. 10. The system 370 includes a firstcontact 372 connected to the output terminals T1 and T2 of the powercell, a second contact 374 connected to the input terminal A of thepower cell, and a third contact 376 connected to the input terminal C ofthe power supply. Each of the contacts 372, 374, 376 include stationaryportions and a movable portion. Although the second and third contacts374, 376 are shown in FIG. 11 as being connected to input terminals Aand C, it will be appreciated that, according to other embodiments, thesecond and third contacts 374, 376 may be connected to any two of theinput terminals A, B and C.

The system 370 also includes a first coil 378 which controls the movableportions of the first contact 372, a second coil 380 which controls themovable portion of the second contact 374, and a third coil 382 whichcontrols the movable portion of the third contact 376. According tovarious embodiments, the coils 378, 380, 372 are embodied as contactorcoils. According to other embodiments, the coils 378, 380, 382 areembodied as magnetic latching coils which do not need to have continuouspower applied to the coils in order to hold the plunger in its first orsecond position and/or to hold the moving portions of the contacts 372,374, 376 in the non-bypass or bypass position.

According to various embodiments, the first contact 372 and the firstcoil 378 are portions of a first bypass device, the second contact 374and the second coil 380 are portions of a second bypass device, and thethird contact 376 and the third coil 382 are portions of a third bypassdevice. For such embodiments, the system 370 includes a plurality ofbypass devices.

In contrast to the system 350 of FIG. 10, the system 370 includes asingle local printed circuit board 384 which is in communication withthe first coil 378, the second coil 380, and the third coil 382. Thelocal printed circuit board 384 is configured to control the respectivemovable portions of the contacts 372, 374, 376 via the respective coils378, 380, 382. Thus, the local printed circuit board 384 is similar tothe local printed circuit boards described with respect to FIG. 10, butis different in that the local printed circuit board 384 is configuredto drive three coils and recognize the respective positions of themovable portions of three contacts. In general, the local printedcircuit board 384 is configured to receive commands from, and reportstatus to, a master control device (e.g., master control system 195 ofFIG. 1) that is held near ground potential.

The local printed circuit board 384 is also configured to deliver pulsesof energy to the coils 378, 380, 382 as needed to change the position ofthe movable portions of the respective contacts 372, 374, 376, and todetect the position of the movable portions of the respective contacts372, 374, 376. The local printed circuit board 384 may obtain controlpower from the input lines which are connected to input terminals A, B,C of the power cell. As shown in FIG. 11, one or more position sensingdevices (labeled PSD in FIG. 11) may be utilized to provide the localprinted circuit board 384 with the respective positions of the movableportions of the contacts 372, 374, 376. According to variousembodiments, the position sensing devices may be embodied as switchingdevices, hall effect sensors, optical sensors, etc.

For embodiments where the coils 378, 380, 382 are latching coils, thelocal printed circuit board 384 may include a DC capacitor which canstore enough energy to switch the plunger and/or the movable portions ofthe contacts 352, 354, 356 between positions. The local printed circuitboard 384 may also include a power supply which restores the storedenergy after a switching event, using AC power from the input linesconnected to the input terminals A, B, C of the power cell.

FIG. 12 illustrates various embodiments of a system 390 for bypassing apower cell (e.g., power cell 210) of a power supply. The system 390 issimilar to the system 370 of FIG. 11. 1he system 390 includes a bypassdevice 392 which may be embodied as a multi-pole contactor. The bypassdevice 392 may be identical to or similar to the bypass device 300 shownin FIGS. 7-9. The bypass device 392 includes a first contact 394connected to the output terminals T1 and T2 of the power cell, a secondcontact 396 connected to the input terminal A of the power cell, and athird contact 398 connected to the input terminal C of the power supply.Each of the contacts 394, 396, 398 include stationary portions and amovable portion. Although the second and third contacts 396, 398 areshown in FIG. 12 as being connected to input terminals A and C, it willbe appreciated that, according to other embodiments, the second andthird contacts 396, 398 may be connected to any two of the inputterminals A, B and C.

In contrast to system 370 of FIG. 11, the system 390 includes a singlecoil 400 which controls the movable portions of the first, second andthird contacts 394, 396, 398. According to various embodiments, the coil400 is embodied as a contactor coil. According to other embodiments, thecoil 400 is embodied as a magnetic latching coil which does not need tohave continuous power applied to the coil in order to hold the plungerin its first or second position and/or to hold the moving portions ofthe contacts 394, 396, 398 in the non-bypass or bypass position.

The system 390 also includes a single local printed circuit board 402which is in communication with the coil 400. The local printed circuitboard 402 is configured to control the respective movable portions ofthe contacts 394, 396, 398 via the coil 400. In general, the localprinted circuit board 402 is configured to receive commands from, andreport status to, a master control device (e.g., master control system195 of FIG. 1) that is held near ground potential.

The local printed circuit board 402 is also configured to deliver pulsesof energy to the coil 400 as needed to change the position of themovable portions of the respective contacts 394, 396, 398, and torecognize the position of the movable portions of the respectivecontacts 394, 396, 398. The local printed circuit board 402 may obtaincontrol power from the input lines which are connected to inputterminals A, B, C of the power cell. As shown in FIG. 12, a positionsensing device (labeled PSD in FIG. 12) may be utilized to provide thelocal printed circuit board 402 with the respective positions of themovable portions of the contacts 394, 396, 398. According to variousembodiments, the position sensing device may be embodied as a switchingdevice, a hall effect sensor, an optical sensor, etc.

For embodiments where the coil 400 is a latching coil, the local printedcircuit board 402 may also include a DC capacitor which can store enoughenergy to switch the plunger and/or the movable portions of the contacts394, 396, 398 between positions. The local printed circuit board 402 mayalso include a power supply which restores the stored energy after aswitching event, using AC power from the input lines connected to theinput terminals A, B, C of the power cell.

FIG. 13 illustrates various embodiments of a circuit 410 for controllinga bypass device (e.g., bypass device 392 of FIG. 12). The circuit 410may be embodied as a printed circuit board having integrated circuits,discrete components, and combinations thereof. The circuit 410 may beutilized, for example, to provide the functionality of one or more ofthe local printed circuit boards described hereinabove. For reasons ofsimplicity, the circuit 410 will be described as a printed circuit boardin the context of its use in the system 390 of FIG. 12.

The circuit board 410 includes an on-board DC control power supply 412.The power supply 412 includes series limiting impedance components Z1,Z2, Z3 and a rectifier 414. The impedance components Z1, Z2, Z3 arerespectively connected to three input lines which are connected to inputterminals A, B, C of a power cell (e.g., power cell 210). The impedancecomponents Z1, Z2, Z3 may be embodied, for example, to includecapacitors, and may be sized such that if one fails, the other two cancontinue to operate to limit the available current. According to variousimplementations, the impedance components Z1, Z2, Z3 may also beembodied to include resistors in series with the capacitors. Accordingto various embodiments, the rectifier 414 is a six-pulse dioderectifier. The printed circuit board 410 also includes a capacitor C1connected to the power supply 412, a group of switching devices 416connected to the capacitor C1, and another regulator 418 connected tothe capacitor C1. As shown in FIG. 13, the group of switching devices416 is also connected to a coil (e.g., coil 400 of the bypass device 392of FIG. 12).

The capacitor C1 is sized to be able to store the amount of energyneeded to cause the plunger and/or the movable portions of the contactsto change positions when such energy is applied to the coil. CapacitorC1 may be embodied as, for example, an electrolytic capacitor, an ultracapacitor, a film type capacitor, etc. Although the capacitor C1 isshown as a single capacitor in FIG. 13, it will be appreciated thatcapacitor C1 may be embodied as multiple capacitors (e.g., threecapacitors) connected in series or parallel.

The group of switching devices 416 is configured to apply either apositive or a negative current pulse to the coil. The individualswitching devices may be embodied as, for example, mosfets, insulatedgate bipolar transistors, etc. Although each coil described herein isdescribed in the context of a single winding for purposes of simplicity,one skilled in the art will appreciate that according to otherembodiments, a given coil can comprise two redundant windings, with onewinding being connected to receive the positive current pulse and theother winding connected to receive the negative current pulse. Thus,although the group of switching devices 416 is shown in FIG. 13 ashaving four individual switching devices, according to otherembodiments, the group of switching devices 416 may include a differentnumber of switching devices (e.g., two switching devices). The regulator418 may be configured to condition the voltage of the power supply 412to operate fiber optic and control circuits.

In operation, the power supply 412 receives AC power from the inputlines connected to the input terminals A, B, C of the power cell. The ACpower flows through the series limiting impedance components Z1, Z2, Z3to the rectifier 414. The rectifier 414 converts the AC power to DCpower, and the DC power charges capacitor C1 to the voltage at V1. Thevoltage at V1 is applied to the group of switching, devices 416, anddepending on the respective states (e.g., on, off) of the individualswitching devices, the group of switching devices 416 may deliver apositive or a negative current pulse to the coil. The positive ornegative current pulses create a magnetic field which is utilized tochange the position of the plunger and/or the movable portions of thecontacts which are connected to the input and output terminals of thepower cell.

When the capacitor C1 is discharging, the group of switching devices 416may employ pulse-width modulation (PWM) to maintain a substantiallyconstant average voltage (or constant current) on the coil. In general,when the capacitor C1 is discharging, the voltage across the capacitorC1 is equal to or greater than approximately one-half of its worst caseinitial voltage. When the coil is a latching coil and none of theswitching devices are in the “on” state, the plunger and/or the movableportions of the contacts may maintain their existing positions bymagnetic latching. During the time that the plunger and/or the movableportions of the contacts maintain their existing positions by magneticlatching, the power supply 412 can recharge the capacitor C1.

In general, the capacitor C1, the group of switching devices 416, thecoil connected to the group of switching devices 416, and the regulator418 should each be rated for the maximum voltage expected to bedelivered to the power cell (i.e., the peak of the input AC line-to-linevoltage delivered to the power cell). Additionally, as the voltage at V1can vary from the maximum voltage delivered to the power cell down toapproximately one-half of the lowest voltage delivered to the power cell(i.e., when capacitor C1 is discharging), the coil should also bedesigned to control the position of the plunger and/or the movableportions of the contacts even when approximately one-half of the lowestvoltage delivered to the power cell is applied to the coil.

With no DC load, the rectifier 414 may generate a DC output voltage atV1 which is substantially equal to the peak of the input line-to-line ACvoltage feeding the power cell. In some embodiments, a power supply mayfunction with power cells having a range of nominal voltage ratings fromabout 630 VAC to about 750 VAC. The power supply may also need totolerate a range of utility voltage from 110% to 70% of nominal. Thus,the peak of the input AC line-to-line voltage (and hence the no-load DCvoltage at V1) may be as high as 1167 volts, and as low as 686 volts.According to other embodiments, other values are possible.

With a short (i.e., line-to-neutral) on the DC output, the DC outputcurrent is effectively limited to approximately 0.55 times the peak ofthe input AC line-to-line voltage, divided by the impedance of theimpedance components Z1, Z2, Z3. For example, if the impedancecomponents Z1, Z2, Z3 are embodied as 0.1 μfd capacitors and the peak ACvoltage is 1167 volts at 60 Hertz, the maximum available DC currentwould be approximately 0.024 amperes. FIGS. 14 and 15 show the per-unitDC current and power available, for various per-unit DC voltages at V1.The per-unit values are based on open-circuit and short-circuit valuesdefined above.

FIG. 16 illustrates various embodiments of a circuit 430 for controllinga bypass device (e.g., bypass device 392 of FIG. 12). The circuit 430 issimilar to the circuit 410 of FIG. 13, and further includes a shuntregulator 432 connected to the rectifier 414 and a diode D1 connected tothe shunt regulator 432. The shunt regulator 432 operates to limit thevoltage on capacitor C1 to a particular voltage (e.g., 400 volts). Forexample, whenever the voltage at V1 exceeds a particular voltage (e.g.,400 volts), the shunt regulator 432 may short out the rectifier 414. Thediode D1 prevents capacitor C1 from discharging into the shunt regulator432.

In general, for such embodiments, the capacitor C1, the group ofswitching devices 416, the coil connected to the group of switchingdevices 416 (e.g., coil 400 of the bypass device 392 of FIG. 12), andthe regulator 418 could each be rated for the particular voltage (e.g.,400 volts) which is less than the maximum voltage expected to bedelivered to the power cell (i.e., the peak of the input AC line-to-linevoltage delivered to the power cell). If the minimum no-load voltageavailable from the diode D1 is, for example, 686 volts, the voltage atV1 would always reach 400 volts for a nominal cell voltage rating as lowas 630 VAC, even with utility variations from 110% to 70% of nominal. Ifthe maximum short-circuit current available from the rectifier 414 islimited to, for example, 0.024 amperes (see FIGS. 14 and 15), no harmoccurs when the rectifier 414 is shorted out by the shunt regulator 432.For such embodiments, as the voltage at V1 can vary from the maximumvoltage (e.g., 400 volts) down to approximately one-half of the maximumvoltage (e.g., 200 volts), the coil should also be designed to controlthe position of the plunger and/or the movable portions of the contactseven when the lowest voltage at V1 is applied to the coil.

FIG. 17 illustrates various embodiments of a circuit 440 for controllinga bypass device (e.g., bypass device 392 of FIG. 12). The circuit 440 issimilar to the circuit 410 of FIG. 13, and further includes a step-downregulator 442 connected to the capacitor C1, and a capacitor C2connected to the step-down regulator 442. The step-down regulator 442operates to step-down the variable voltage at V1 to a lower fixedvoltage at V2. As the voltage applied to the group of switches 416, thecoil connected to the group of switches 416 (e.g., coil 400 of thebypass device 392 of FIG. 12), and the regulator 418 is the lowervoltage at V2, the group of switching devices 416, the coil, and theregulator 418 may each be rated for the lower voltage. According tovarious embodiments, the voltage at V2 may be low enough to allow forthe use of integrated circuits for the group of switches 416 and theregulator 418. Even if the voltage at V1 sags significantly while thecapacitor C1 discharges its stored energy, the voltage at V2 could beheld nearly constant, provided that the voltage provided by thestep-down regulator 442 is less than the minimum voltage that appearedat V1 during the sag. For such embodiments, pulse width modulationcontrol of the switching devices of the H-bridge 416 is not necessary.

FIG. 18 illustrates various embodiments of a circuit 450 for controllinga bypass device (e.g., bypass device 392 of FIG. 12). The circuit 450 issimilar to the circuit 410 of FIG. 13, and further includes a shuntregulator 432 connected to the rectifier 414, a diode D1 connected tothe shunt regulator 432, a step-down regulator 442 connected to thecapacitor C1, and a capacitor C2 connected to the step-down regulator442. The added components operate as described in FIGS. 16 and 17, andsuch operation can result in the voltage at V1 being, for example,between 200 volts DC and 400 volts DC. For such embodiments, the lowerDC voltages at V1 would reduce the peak voltage stress on the shuntregulator 432, the capacitor C1, and the step-down regulator 442. Forexample, the peak voltage stress on the shunt regulator 432, thecapacitor C1, and the step-down regulator 442 may be reduced from 1167volts DC to 400 volts DC. The voltage at V2 could be held nearlyconstant, at a low value. For such embodiments, pulse width modulationcontrol of the group of switching devices 416 is not necessary, andintegrated circuits can be utilized for the group of switches 416 andthe regulator 418. Also, the amount of insulation needed for the coilconnected to the group of switching devices 416 (e.g., coil 400 of thebypass device 392 of FIG. 12) could be reduced.

FIG. 19 illustrates various embodiments of a circuit 460 for controllinga plurality of bypass devices (e.g., the bypass devices of FIG. 11). Thecircuit 460 is similar to the circuit 450 of FIG. 18, but includes threegroups of switching devices 416, 462, 464 which are each connected tothe capacitor C2. The additional groups of switching devices 462, 464are similar to the group of switching devices 416 as describedhereinabove. Each of the groups of switching devices 416, 462, 464 arealso connected to a different coil (e.g., coils 378, 380, 382 of FIG.11) which forms a portion of a different bypass device. Thus, oneskilled in the art will appreciate that the circuit 460 may be utilized,for example, to provide the functionality of the local printed circuitboard 384 of FIG. 11, which controls the three coils 378, 380, 382 whichcontrol the respective positions of the plunger and/or the movableportions of contacts 372, 374, 376. For such embodiments, the capacitorC1 is sized to be able to store the amount of energy needed to cause theplunger and/or the movable portions of all the contacts to concurrentlychange positions when such energy is applied to all the coils.

While several embodiments of the invention have been described herein byway of example, those skilled in the art will appreciate that variousmodifications, alterations, and adaptions to the described embodimentsmay be realized without departing from the spirit and scope of theinvention defined by the appended claims.

1. A system, comprising: a multi-winding device having a primary windingand a plurality of three-phase secondary windings; a plurality of powercells, wherein each power cell is connected to a different three-phasesecondary winding of the multi-winding device; a first contact connectedto a first input terminal of at least one of the power cells; a secondcontact connected to a second input terminal of the at least one of thepower cells; and a third contact connected to first and second outputterminals of the at least one of the power cells.
 2. The system of claim1, further comprising: a first coil coupled to a movable portion of thefirst contact; a second coil coupled to a movable portion of the secondcontact; and a third coil coupled to a movable portion of the thirdcontact.
 3. The system of claim 2, wherein at least one of the first,second and third coils is a latching coil.
 4. The system of claim 2,further comprising a control circuit connected to at least one of thefirst, second and third coils.
 5. The system of claim 4, wherein thecontrol circuit is connected to the three-phase secondary winding towhich the at least one of the power cells is connected.
 6. The system ofclaim 4, wherein the control circuit comprises a printed circuit board.7. The system of claim 4, wherein the control circuit comprises: animpedance component connected to the three-phase secondary winding towhich the at least one of the power cells is connected; a rectifierconnected to the impedance component; a capacitor connected to therectifier; and a group of switching devices connected to the capacitorand at least one of the first, second and third coils.
 8. The system ofclaim 7, wherein the rectifier is a six-pulse rectifier.
 9. The systemof claim 7, wherein the group of switching devices is an integratedcircuit.
 10. The system of claim 7, further comprising a secondregulator connected to the capacitor.
 11. The system of claim 10,wherein the second regulator is an integrated circuit.
 12. The system ofclaim 7, further comprising: a shunt regulator connected to therectifier; and a diode connected between the shunt regulator and thecapacitor.
 13. The system of claim 7, further comprising: a step-downregulator connected to the capacitor; and a second capacitor connectedbetween the step-down regulator and the group of switching devices. 14.The system of claim 7, further comprising: a shunt regulator connectedto the rectifier; a diode connected between the shunt regulator and thecapacitor; a step-down regulator connected to the capacitor; and asecond capacitor connected between the step-down regulator and the groupof switching devices.
 15. The system of claim 4, further comprising aswitching device connected to the control circuit and at least one ofthe coils.
 16. A system, comprising: a multi-winding device having aprimary winding and a plurality of three-phase secondary windings; aplurality of power cells, wherein each power cell is connected to adifferent three-phase secondary winding of the multi-winding device; afirst contactor connected to a first input terminal of at least one ofthe power cells; a second contactor connected to a second input terminalof the at least one of the power cells; and a third contactor connectedto first and second output terminals of the at least one of the powercells.
 17. The system of claim 16, wherein: the first contactorcomprises a first coil; the second contactor comprises a second coil;and the third contactor comprises a third coil.
 18. The system of claim16, further comprising a control circuit connected to at least one ofthe first, second and third contactors.
 19. The system of claim 18,wherein the control circuit comprises a printed circuit board.
 20. Thesystem of claim 18, wherein the control circuit comprises: an impedancecomponent connected to the three-phase secondary winding to which the atleast one of the power cells is connected; a rectifier connected to theimpedance component; a capacitor connected to the rectifier; and a groupof switching devices connected to the capacitor and at least one of thefirst, second and third coils.